1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system, and to a head assembly and a hard disk drive each of which includes such a magnetic head for perpendicular magnetic recording.
2. Description of the Related Art
For magnetic read/write devices such as magnetic disk drives, higher recording density has been constantly required to achieve a higher storage capacity and smaller dimensions. Typically, magnetic heads used in magnetic read/write devices are those having a structure in which a reproducing (read) head having a magnetoresistive element (that may be hereinafter referred to as an MR element) for reading and a recording (write) head having an induction-type electromagnetic transducer for writing are stacked on a substrate.
Write heads include those of a longitudinal magnetic recording system wherein signals are magnetized in the direction along the surface of the recording medium (the longitudinal direction) and those of a perpendicular magnetic recording system wherein signals are magnetized in the direction perpendicular to the surface of the recording medium. Recently, the shift from the longitudinal magnetic recording system to the perpendicular magnetic recording system has been promoted in order to achieve higher recording density of magnetic read/write devices.
A write head for the perpendicular magnetic recording system includes a coil for generating a magnetic field corresponding to data to be written on the recording medium, and a pole layer for allowing a magnetic flux corresponding to the magnetic field generated by the coil to pass therethrough and generating a write magnetic field for writing the data on the recording medium. The pole layer has an end located in a medium facing surface, and the width of this end defines the track width.
The pole layer includes, for example, a track width defining portion having a first end located in the medium facing surface and a second end opposite to the first end, and a wide portion coupled to the second end of the track with defining portion and having a width greater than that of the track width defining portion. The track width defining portion has a nearly uniform width. The width of the first end of the track width defining portion defines the track width. The wide portion has two front end faces that are located at outer positions relative to the track width defining portion along the track width direction and that face toward the medium facing surface.
A magnetic head used for a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air-inflow-side end and an air-outflow-side end. The slider slightly flies over the surface of the recording medium by means of the airflow that comes from the air-inflow-side end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air-outflow-side end of the medium facing surface of the slider. In a magnetic disk drive, the magnetic head is aligned through the use of a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit centered on the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs according to the position of the magnetic head across the tracks.
In a magnetic disk drive of the perpendicular magnetic recording system that exhibits a better capability of writing on a recording medium than the longitudinal magnetic recording system, in particular, if the above-mentioned skew occurs, there arise problems such as a phenomenon in which, when data is written on a specific track, data stored on a track adjacent thereto is erased (that is hereinafter referred to as adjacent track erase), or unwanted writing between two adjacent tracks. To achieve higher recording density, it is required to suppress adjacent track erase. Unwanted writing between two adjacent tracks affects detection of servo signals for alignment of the magnetic head and the signal-to-noise ratio of a read signal.
One of causes of the occurrences of the above-mentioned adjacent track erase and unwanted writing is flux leakage occurring in a portion of the medium facing surface other than the end face of the pole layer. Such flux leakage occurs because of a magnetic flux that leaks from the front end faces of the wide portion to the outside of the pole layer and then reaches the medium facing surface. To prevent the problems resulting from such flux leakage, a possible measure is to reduce the value of current fed to the coil. However, this will cause degradation in write characteristics such as an overwrite property that is a parameter indicating an overwriting capability. On the other hand, if an attempt is made to improve write characteristics, the above-mentioned flux leakage can increase and the problems resulting from the flux leakage will be encountered.
JP 2003-006814A discloses a magnetic head including: a bottom pole; a top pole that is opposed to the bottom pole in a front gap portion with a gap layer disposed in between and that touches the bottom pole in a back gap portion; a pole tip portion that partially touches the top pole and that is opposed to the bottom pole with a write gap layer disposed in between; and a coil. In this magnetic head, the coil is helically wound around the top pole and the pole tip portion. In this magnetic head, however, the coil does not have any portion located between the medium facing surface and the end face of the top pole facing toward the medium facing surface. Because of this, in the magnetic head, a magnetic flux leaking from the end face of the top pole and reaching the medium facing surface is likely to occur. This magnetic head is therefore incapable of sufficiently suppressing the foregoing problems resulting from the flux leakage.